Color and photographic film processing has come into widespread use, particularly in medical facilities where non-invasive x-ray imaging techniques have become a standard diagnostic tool in dentistry, medical and veterinary care. A radiograph or radio sensitive film is a photographic film capable of registering an image when exposed to radiant energy of extremely short wavelength, for example, about 0.0001 the wavelength of light. Radiographic or x-ray film is made of an emulsion (gelatin containing a silver compound) and a transparent, blue tinted base. The base of this photosensitive film is made from a cellulose derivative usually cellulose acetate which provides the desired degree of stiffness and flatness for handling. The sensitive emulsion is made up of many grains or crystals of silver bromide or other silver halide material in a gelatin, and the emulsion is generally coated on both sides of the base.
Upon exposure, the radiosensitive film must be processed to make the image visible and permanent. Processing consists of developing, rinsing, fixing, washing and drying. Accordingly, the film must be placed in a developer solution to convert the invisible image to a visible one composed of minute masses of black metallic silver. After contact with a developer, the film must be rinsed to remove excess developing solution and prevent fixer contamination. Next the film must be placed in a fixing solution to remove the unexposed silver halide therefrom and then be washed again to remove the processing chemicals and prevent eventual discoloration and fading. The film is then dried.
Difficulties are experienced when dealing with disposal of fixer and developer solutions after processing. EPA Regulations 40 CFR .sctn..sctn.122 and 403 (Jul. 24, 1990) prohibit developer and fixer fluids from being introduced into waste water treatment systems. These prohibitions are based on two broad areas of contamination. The first contaminant is the silver in fixer fluids. Typical x-ray fluids contain 3.2 or more milligrams of silver per liter of fixer. This is more than 64 times the allowable concentration in waste water of 0.05 milligrams per liter. In fact, the EPA Guide to Pollution Prevention (EPA 625/70-90 CO9, page 5) confirms that photographic chemicals are hazardous materials that should not be discharged into waste water treatment systems even if allowed by local sanitary authorities.
Fixer and developer solutions are also considered "contaminants" in that both the developer and fixer fluids are reactives. The developer fluid is a reducing agent and the reactive fixer is an oxidizing agent. EPA waste water standards prohibit the entry of "reactives" into a waste water treatment facility.
It is thus an object of the present invention to provide a means of "decontaminating" fixer and developer solutions and precipitating the silver ion as silver sulfide, an insoluble and nontoxic form of the metal.
It is yet a further object of the present invention to provide a method of disposing fixers and developers by rendering such solutions nonreactive.
It is yet a further object of the present invention to provide a method for disposing of fixer and developer solutions by immobilizing these solutions and binding them in a system which enables the mixture to be disposed of in a landfill or similar site designed to receive nonhazardous waste.
These and further objects of the present invention will be more readily appreciated with considering the following disclosure and appended claims.